Commit message: crypto: algif_skcipher - Load TX SG list after waiting

commit 4f0414e54e4d1893c6f08260693f8ef84c929293 upstream.

We need to load the TX SG list in sendmsg(2) after waiting for
incoming data, not before.

[connoro@google.com: backport to 3.18, where the relevant logic is
located in skcipher_recvmsg() rather than skcipher_recvmsg_sync()]

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Connor O'Brien <connoro@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CVE: CVE-2017-13215
CWE: NVD-CWE-noinfo
Vulnerability description: A elevation of privilege vulnerability in the Upstream kernel skcipher. Product: Android. Versions: Android kernel. Android ID: A-64386293. References: Upstream kernel.

Project: linux-stable
File: algif_skcipher.c

static void skcipher_data_wakeup(struct sock *sk)
{
	struct alg_sock *ask = alg_sk(sk);
	struct skcipher_ctx *ctx = ask->private;
	struct socket_wq *wq;

	if (!ctx->used)
		return;

	rcu_read_lock();
	wq = rcu_dereference(sk->sk_wq);
	if (wq_has_sleeper(wq))
		wake_up_interruptible_sync_poll(&wq->wait, POLLOUT |
							   POLLRDNORM |
							   POLLRDBAND);
	sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
	rcu_read_unlock();
}

Project: linux-stable
File: algif_skcipher.c

static ssize_t skcipher_sendpage_nokey(struct socket *sock, struct page *page,
				       int offset, size_t size, int flags)
{
	int err;

	err = skcipher_check_key(sock);
	if (err)
		return err;

	return skcipher_sendpage(sock, page, offset, size, flags);
}

Project: linux-stable
File: algif_skcipher.c

static int skcipher_alloc_sgl(struct sock *sk)
{
	struct alg_sock *ask = alg_sk(sk);
	struct skcipher_ctx *ctx = ask->private;
	struct skcipher_sg_list *sgl;
	struct scatterlist *sg = NULL;

	sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);
	if (!list_empty(&ctx->tsgl))
		sg = sgl->sg;

	if (!sg || sgl->cur >= MAX_SGL_ENTS) {
		sgl = sock_kmalloc(sk, sizeof(*sgl) +
				       sizeof(sgl->sg[0]) * (MAX_SGL_ENTS + 1),
				   GFP_KERNEL);
		if (!sgl)
			return -ENOMEM;

		sg_init_table(sgl->sg, MAX_SGL_ENTS + 1);
		sgl->cur = 0;

		if (sg) {
			scatterwalk_sg_chain(sg, MAX_SGL_ENTS + 1, sgl->sg);
			sg_unmark_end(sg + (MAX_SGL_ENTS - 1));
		}

		list_add_tail(&sgl->list, &ctx->tsgl);
	}

	return 0;
}

Project: linux-stable
File: algif_skcipher.c

static void *skcipher_bind(const char *name, u32 type, u32 mask)
{
	struct skcipher_tfm *tfm;
	struct crypto_ablkcipher *skcipher;

	tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
	if (!tfm)
		return ERR_PTR(-ENOMEM);

	skcipher = crypto_alloc_ablkcipher(name, type, mask);
	if (IS_ERR(skcipher)) {
		kfree(tfm);
		return ERR_CAST(skcipher);
	}

	tfm->skcipher = skcipher;

	return tfm;
}

Project: linux-stable
File: algif_skcipher.c

static int skcipher_recvmsg(struct kiocb *unused, struct socket *sock,
			    struct msghdr *msg, size_t ignored, int flags)
{
	struct sock *sk = sock->sk;
	struct alg_sock *ask = alg_sk(sk);
	struct skcipher_ctx *ctx = ask->private;
	unsigned bs = crypto_ablkcipher_blocksize(crypto_ablkcipher_reqtfm(
		&ctx->req));
	struct skcipher_sg_list *sgl;
	struct scatterlist *sg;
	unsigned long iovlen;
	struct iovec *iov;
	int err = -EAGAIN;
	int used;
	long copied = 0;

	lock_sock(sk);
	for (iov = msg->msg_iov, iovlen = msg->msg_iovlen; iovlen > 0;
	     iovlen--, iov++) {
		unsigned long seglen = iov->iov_len;
		char __user *from = iov->iov_base;

		while (seglen) {
			used = ctx->used;
			if (!used) {
				err = skcipher_wait_for_data(sk, flags);
				if (err)
					goto unlock;
			}

			used = min_t(unsigned long, used, seglen);

			used = af_alg_make_sg(&ctx->rsgl, from, used, 1);
			err = used;
			if (err < 0)
				goto unlock;

			if (ctx->more || used < ctx->used)
				used -= used % bs;

			err = -EINVAL;
			if (!used)
				goto free;

			sgl = list_first_entry(&ctx->tsgl,
					       struct skcipher_sg_list, list);
			sg = sgl->sg;

			while (!sg->length)
				sg++;

			ablkcipher_request_set_crypt(&ctx->req, sg,
						     ctx->rsgl.sg, used,
						     ctx->iv);

			err = af_alg_wait_for_completion(
				ctx->enc ?
					crypto_ablkcipher_encrypt(&ctx->req) :
					crypto_ablkcipher_decrypt(&ctx->req),
				&ctx->completion);

free:
			af_alg_free_sg(&ctx->rsgl);

			if (err)
				goto unlock;

			copied += used;
			from += used;
			seglen -= used;
			skcipher_pull_sgl(sk, used);
		}
	}

	err = 0;

unlock:
	skcipher_wmem_wakeup(sk);
	release_sock(sk);

	return copied ?: err;
}

Project: linux-stable
File: algif_skcipher.c

static int skcipher_sendmsg_nokey(struct kiocb *unused, struct socket *sock,
				  struct msghdr *msg, size_t size)
{
	int err;

	err = skcipher_check_key(sock);
	if (err)
		return err;

	return skcipher_sendmsg(NULL, sock, msg, size);
}

Project: linux-stable
File: algif_skcipher.c

static int skcipher_setkey(void *private, const u8 *key, unsigned int keylen)
{
	struct skcipher_tfm *tfm = private;
	int err;

	err = crypto_ablkcipher_setkey(tfm->skcipher, key, keylen);
	tfm->has_key = !err;

	return err;
}

Project: linux-stable
File: algif_skcipher.c

static ssize_t skcipher_sendpage(struct socket *sock, struct page *page,
				 int offset, size_t size, int flags)
{
	struct sock *sk = sock->sk;
	struct alg_sock *ask = alg_sk(sk);
	struct skcipher_ctx *ctx = ask->private;
	struct skcipher_sg_list *sgl;
	int err = -EINVAL;

	if (flags & MSG_SENDPAGE_NOTLAST)
		flags |= MSG_MORE;

	lock_sock(sk);
	if (!ctx->more && ctx->used)
		goto unlock;

	if (!size)
		goto done;

	if (!skcipher_writable(sk)) {
		err = skcipher_wait_for_wmem(sk, flags);
		if (err)
			goto unlock;
	}

	err = skcipher_alloc_sgl(sk);
	if (err)
		goto unlock;

	ctx->merge = 0;
	sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);

	get_page(page);
	sg_set_page(sgl->sg + sgl->cur, page, size, offset);
	sgl->cur++;
	ctx->used += size;

done:
	ctx->more = flags & MSG_MORE;
	if (!ctx->more && !list_empty(&ctx->tsgl))
		sgl = list_entry(ctx->tsgl.prev, struct skcipher_sg_list, list);

unlock:
	skcipher_data_wakeup(sk);
	release_sock(sk);

	return err ?: size;
}

Project: linux-stable
File: algif_skcipher.c

static void skcipher_release(void *private)
{
	struct skcipher_tfm *tfm = private;

	crypto_free_ablkcipher(tfm->skcipher);
	kfree(tfm);
}

Project: linux-stable
File: algif_skcipher.c

static int skcipher_accept_parent_nokey(void *private, struct sock *sk)
{
	struct skcipher_ctx *ctx;
	struct alg_sock *ask = alg_sk(sk);
	struct skcipher_tfm *tfm = private;
	struct crypto_ablkcipher *skcipher = tfm->skcipher;
	unsigned int len = sizeof(*ctx) + crypto_ablkcipher_reqsize(skcipher);

	ctx = sock_kmalloc(sk, len, GFP_KERNEL);
	if (!ctx)
		return -ENOMEM;

	ctx->iv = sock_kmalloc(sk, crypto_ablkcipher_ivsize(skcipher),
			       GFP_KERNEL);
	if (!ctx->iv) {
		sock_kfree_s(sk, ctx, len);
		return -ENOMEM;
	}

	memset(ctx->iv, 0, crypto_ablkcipher_ivsize(skcipher));


	INIT_LIST_HEAD(&ctx->tsgl);
	ctx->len = len;
	ctx->used = 0;
	ctx->more = 0;
	ctx->merge = 0;
	ctx->enc = 0;
	af_alg_init_completion(&ctx->completion);

	ask->private = ctx;

	ablkcipher_request_set_tfm(&ctx->req, skcipher);
	ablkcipher_request_set_callback(&ctx->req, CRYPTO_TFM_REQ_MAY_BACKLOG,
					af_alg_complete, &ctx->completion);

	sk->sk_destruct = skcipher_sock_destruct;

	return 0;
}

Project: linux-stable
File: algif_skcipher.c

static int skcipher_check_key(struct socket *sock)
{
	int err = 0;
	struct sock *psk;
	struct alg_sock *pask;
	struct skcipher_tfm *tfm;
	struct sock *sk = sock->sk;
	struct alg_sock *ask = alg_sk(sk);

	lock_sock(sk);
	if (ask->refcnt)
		goto unlock_child;

	psk = ask->parent;
	pask = alg_sk(ask->parent);
	tfm = pask->private;

	err = -ENOKEY;
	lock_sock_nested(psk, SINGLE_DEPTH_NESTING);
	if (!tfm->has_key)
		goto unlock;

	if (!pask->refcnt++)
		sock_hold(psk);

	ask->refcnt = 1;
	sock_put(psk);

	err = 0;

unlock:
	release_sock(psk);
unlock_child:
	release_sock(sk);

	return err;
}

Project: linux-stable
File: algif_skcipher.c

static int skcipher_accept_parent(void *private, struct sock *sk)
{
	struct skcipher_tfm *tfm = private;

	if (!tfm->has_key)
		return -ENOKEY;

	return skcipher_accept_parent_nokey(private, sk);
}

Project: linux-stable
File: algif_skcipher.c

static int skcipher_recvmsg_nokey(struct kiocb *unused, struct socket *sock,
				  struct msghdr *msg, size_t ignored, int flags)
{
	int err;

	err = skcipher_check_key(sock);
	if (err)
		return err;

	return skcipher_recvmsg(NULL, sock, msg, ignored, flags);
}